Cyclone alerts

Figure 1. Google Maps displays a storm forecast geometry.

Public Alerts can display a tropical storm forecast geometry on Google Maps like the one shown in figure 1 if you follow these requirements:

1. Provide a valid CAP alert in your feed that contains the cyclone information.

2. In a new, non-CAP feed, provide additional data that specifies the storm geometry associated with the storm information in the CAP alert.

Additional requirements for a cyclone CAP alert

For alerts on tropical storm, typhoon, and cyclone event types, you must specify a unique storm ID in the CAP alert. We recommend that you use the <info> and <parameter> elements to assign an enumeration value of StormId in the <valueName> element, as shown in the following code snippet.

<parameter>
    <valueName>StormId</valueName>
    <value>UniqueStormId</value>
</parameter>

Public Alerts uses this information to connect the storm to the right visualization in the storm geometry feed.

Example

<parameter>
    <valueName>StormId</valueName>
    <value>UIG4354812</value>
</parameter>

Additional requirements for storm geometry information feeds

If your feed includes storm geometry data, prepare a second feed file that contains information about the different tropical storms. Include the URLs for the data files that contain the forecast geometry. NOAA produces a forecast geometry feed that contains data in XML format like in the following code example:

<item>
  <title>
    Advisory #024 Forecast [shp] - Tropical Storm Walaka (CP1/CP012018)
  </title>
  <description>
    Forecast Track, Cone of Uncertainty, Watches/Warnings. Shapefile last
     updated 05 Oct 2018 14:52:04 GMT.
  </description>
<link>http://www.prh.noaa.gov/cphc/tc_graphics/2018/gis/cp012018_5day_024.zip
  </link>
</item>

In the preceding example, the <link> element includes a ZIP file that contains files which represent the forecast geometry of the mentioned tropical storm. Include the following files in your feed's ZIP file:

• A file that contains the storm center forecast points.
• A file that contains the center forecast track line.
• A file that contains the forecast cone polygon.

To differentiate the ZIP files while they process, each file must have a different filename suffix.

Important: One of your feed's ZIP files must contain a field that identifies the unique ID of the storm (the StormID value). We recommend that you include this ID in the storm center forecast points file. We also recommend that the forecast contains the time when the forecast starts and the time when it expires.

For example, the NHC forecast file al012021_5day_001.zip contains the following files:

• al012021-001_5day_lin.shp
• al012021-001_5day_pgn.shp
• al012021-001_5day_pts.shp
• al012021-001_ww_wwlin.shp

The attribute table for al012021-001_ww_wwlin.shp contains a column named STORMNUM (see figure 2). Data in that column is used as the StormID value in the feed.

Figure 2. Provide StormID values in the STORMNUM column.

The attribute table for al012021-001_5day_pts.shp uses columns named LAT and LON to denote the latitude and longitude information, respectively (see figure 3).

Figure 3. Provide latitude and longitude data in the LAT and LON columns.

Tropical storm geometry checklist

Before you submit your feed to Google to support tropical storm cone geometry, complete the following checklist:

☐ Produce a valid CAP alert with a unique StormId value.
☐ Produce a feed for forecast geometry, and share its URL with Google.
☐ Send an explanation of the structure of the ZIP file that contains your forecast geometry:
    ☐ Which file specifies the storm center forecast points?
    ☐ Which file specifies the center forecast track line?
    ☐ Which file specifies the forecast cone polygon?
    ☐ Which column names denote the storm ID, latitude, and longitude?